U.S. patent application number 11/768021 was filed with the patent office on 2008-05-29 for transfer mechanism and image forming apparatus using the same.
Invention is credited to Junya MASUDA, Kazuhiro MATSUYAMA, Hiroyuki MURAI, Toshihiko SEIKE, Toshiki TAKIGUCHI.
Application Number | 20080124139 11/768021 |
Document ID | / |
Family ID | 39463861 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080124139 |
Kind Code |
A1 |
MURAI; Hiroyuki ; et
al. |
May 29, 2008 |
TRANSFER MECHANISM AND IMAGE FORMING APPARATUS USING THE SAME
Abstract
A transfer mechanism includes: a transfer unit having a transfer
belt; and a belt contact and separation assembly for bringing the
transfer belt into, and separating it away from, an electrostatic
latent image support by shifting the position of the transfer unit.
The belt contact and separation assembly includes:a multiple number
of transfer unit shifters that abut the transfer unit and shift the
position of the transfer unit; a multiple number of linkage members
that link with the plural transfer unit shifters, correspondingly;
an elastic member for coupling the plural linkage members; and a
driver for actuating the transfer unit shifters through the linkage
members.
Inventors: |
MURAI; Hiroyuki;
(Yamatokoriyama-shi, JP) ; TAKIGUCHI; Toshiki;
(Yamatokoriyama-shi, JP) ; MASUDA; Junya;
(Ikoma-gun, JP) ; SEIKE; Toshihiko; (Nara-shi,
JP) ; MATSUYAMA; Kazuhiro; (Ikoma-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
39463861 |
Appl. No.: |
11/768021 |
Filed: |
June 25, 2007 |
Current U.S.
Class: |
399/313 |
Current CPC
Class: |
G03G 15/167 20130101;
G03G 2215/0193 20130101; G03G 2215/1623 20130101 |
Class at
Publication: |
399/313 |
International
Class: |
G03G 15/20 20060101
G03G015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 2006 |
JP |
2006-174877 |
Jun 29, 2006 |
JP |
2006-179536 |
Claims
1. A transfer mechanism comprising: a transfer unit having a
transfer belt; and, a belt contact and separation assembly for
bringing the transfer belt into, and separating it away from, an
electrostatic latent image support by shifting the position of the
transfer unit, characterized in that the belt contact and
separation assembly includes: a plurality of transfer unit shifters
that abut the transfer unit and shift the position of the transfer
unit; a plurality of linkage members that link with the plural
transfer unit shifters, correspondingly; an elastic member for
coupling the plural linkage members; and a driver for actuating the
transfer unit shifters through the linkage members.
2. The transfer mechanism according to claim 1, wherein the driver
is a solenoid.
3. The transfer mechanism according to claim 1, wherein the
transfer unit shifter makes rotational movement as the driver
operates.
4. The transfer mechanism according to claim 1, wherein the driving
force of the driver is directly transmitted to a first one of the
plural transfer unit shifters, and the driving force is indirectly
transmitted to the transfer unit shifters other than the first
transfer unit shifter, by way of the elastic member.
5. The transfer mechanism according to claim 1, wherein the
transfer unit shifters are actuated by the driving force of the
driver to shift the transfer unit up and down, so as to bring the
transfer unit into contact with and separate it away from, the
electrostatic latent image support.
6. The transfer mechanism according to claim 1, wherein the
transfer unit shifters are arranged at both side ends of the width
of the transfer belt of the transfer unit.
7. The transfer mechanism according to claim 1, wherein, when the
transfer belt is set at the home position for separation in which
the transfer belt is kept away from the electrostatic latent image
support, the first transfer unit shifter arranged close to the
driver is positioned a first distance away from the electrostatic
latent image support; the second transfer unit shifter arranged
farther from the driver than the first transfer unit shifter is
positioned a second distance away from the electrostatic latent
image support; and, the second distance is shorter than the first
distance.
8. The transfer mechanism according to claim 7, wherein, at the
home position for separation, the transfer belt is separated from
the electrostatic latent image support, keeping a uniform gap
distance across the full length of the transfer belt.
9. The transfer mechanism according to claim 8, further comprising
a holding member for holding the transfer unit in order to assure
the uniform gap distance.
10. The transfer mechanism according to claim 8, wherein the
uniform gap distance is at least a distance that prohibits the
residual toner on the electrostatic latent image support from
transferring to the transfer belt under the influence of the
electric field applied to the transfer belt.
11. An image forming apparatus for producing image output in
accordance with a print request, comprising: an image forming
portion having an electrostatic latent image support on which a
developer image is formed with a developer; a transfer mechanism
for transferring the developer image to the transfer belt side;
and, a fixing unit for fixing the developer image transferred by
the transfer mechanism, onto the recording medium, characterized in
that the transfer mechanism comprises: a transfer unit having a
transfer belt; and, a belt contact and separation assembly for
bringing the transfer belt into, and separating it away from, an
electrostatic latent image support by shifting the position of the
transfer unit, and the belt contact and separation assembly
includes: a plurality of transfer unit shifters that abut the
transfer unit and shift the position of the transfer unit; a
plurality of linkage members that link with the plural transfer
unit shifters, correspondingly; an elastic member for coupling the
plural linkage members; and a driver for actuating the transfer
unit shifters through the linkage members.
12. The image forming apparatus according to claim 11, wherein the
driver is a solenoid.
13. The image forming apparatus according to claim 11, wherein the
transfer unit shifter makes rotational movement as the driver
operates.
14. The image forming apparatus according to claim 11, wherein the
driving force of the driver is directly transmitted to a first one
of the plural transfer unit shifters, and the driving force is
indirectly transmitted to the transfer unit shifters other than the
first transfer unit shifter, by way of the elastic member.
15. The image forming apparatus according to claim 11, wherein the
transfer unit shifters are actuated by the driving force of the
driver to shift the transfer unit up and down, so as to bring the
transfer unit into contact with and separate it away from, the
electrostatic latent image support.
16. The image forming apparatus according to claim 11, wherein the
transfer unit shifters are arranged at both side ends of the width
of the transfer belt of the transfer unit.
17. The image forming apparatus according to claim 11, wherein,
when the transfer belt is set at the home position for separation
in which the transfer belt is kept away from the electrostatic
latent image support, the first transfer unit shifter arranged
close to the driver is positioned a first distance away from the
electrostatic latent image support; the second transfer unit
shifter arranged farther from the driver than the first transfer
unit shifter is positioned a second distance away from the
electrostatic latent image support; and, the second distance is
shorter than the first distance.
18. The image forming apparatus according to claim 17, wherein, at
the home position for separation, the transfer belt is separated
from the electrostatic latent image support, keeping a uniform gap
distance across the full length of the transfer belt.
19. The image forming apparatus according to claim 18, wherein the
transfer mechanism further comprises a holding member for holding
the transfer unit in order to assure the uniform gap distance.
20. The image forming apparatus according to claim 18, wherein the
uniform gap distance is at least a distance that prohibits the
residual toner on the electrostatic latent image support from
transferring to the transfer belt under the influence of the
electric field applied to the transfer belt.
Description
[0001] This Nonprovisional application claims priority under 35
U.S.C. .sctn.119(a) on Patent Application No. 2006-174877 filed in
Japan on 26 Jun. 2006 and Patent Application No. 2006-179536 filed
in Japan on 29 Jun. 2006, the entire contents of which are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates to a transfer mechanism and an
image forming apparatus using the same, and in particular, relates
to a transfer mechanism which is used in an image forming apparatus
that is applied to a copier, multi-functional machine, printer,
facsimile machine and the like that uses electrophotography and
outputs images in accordance with print requests, as well as to an
image forming apparatus using this transfer mechanism.
[0004] (2) Description of the Prior Art
[0005] A typical transfer mechanism for use in an image forming
apparatus has a function of transferring image information (toner
image or developer image) that was developed on an electrostatic
latent image support (photoreceptor drum), to a recording medium
(paper) being conveyed, by bringing the paper into contact with the
photoreceptor drum while applying a transfer electric field to the
paper from the rear side of the paper.
[0006] In recent years, with the trend of image forming apparatus
towards becoming compact and high-speed in configurations, use of a
belt transfer system using an endless belt as a transfer mechanism
has been increasingly developed.
[0007] The belt transfer system is constructed such that an endless
belt is used to convey the paper while the paper or the endless
belt is brought into contact with a photoreceptor drum to thereby
transfer the toner image visualized on photoreceptor drum to the
paper or endless belt. In most cases, the belt transfer system is
provided in the form that includes a belt contact and separation
mechanism for moving the endless belt into and out of contact with
the photoreceptor drum.
[0008] Actually, during the transfer stage, the paper or the
endless belt is brought into contact with the photoreceptor drum,
but during the non-transfer stage, the belt needs to be kept out of
contact with the photoreceptor drum so as to prevent the endless
belt from being worn out or deteriorated.
[0009] To deal with this, there has been a known technique, as a
conventional belt contact and separation mechanism, which uses a
cam mechanism to move the transfer unit relative to the
photoreceptor drum (see patent document 1: Japanese Patent
Application Laid-open H08-137166). Illustratively, an endless belt
(transfer belt), a multiple number of rollers that support the belt
and a transfer roller are assembled as a single transfer unit, and
this transfer unit as a whole is moved into and out of contact with
the photoreceptor drum by a cam system.
[0010] However, since the above cam mechanism is configured to be
driven by actuating cams by manually rotating a handle, it needs a
complicated drive coupling technique. Further, since the transfer
unit is manually moved up and down, there is the problem of poor
response when it is applied to a high-speed printing process.
[0011] To avoid this problem there is a method of moving the
transfer unit as a whole by using, as a drive source, a solenoid
which presents excellent operational response. In this case, a
multiple number of cams are arranged in series along the width
direction of the transfer belt, and the multiple cams coupled in
series are operated by switching on and off a single solenoid.
[0012] However, in the above method using a solenoid, there occur
some cases in which contact and separation between the transfer
belt and the photoreceptor drum cannot be achieved smoothly due to
an operational delay of the cam or cams located on the far side
from the solenoid depending on the assembly and/or machining
accuracy. For example, there occurs a case in which the transfer
belt comes into contact with the photoreceptor drum on the side
near to the solenoid while it remains away from the photoreceptor
drum on the side far from the solenoid.
SUMMARY OF THE INVENTION
[0013] The present invention has been devised in view of the above
conventional problems, it is therefore an object of the present
invention to provide a transfer mechanism of a belt system which
can assure correct operation of contact and separation between a
photoreceptor drum and a transfer belt in the transfer
mechanism.
[0014] The transfer mechanism according to the present invention
for solving the above problems are configured as follows.
[0015] A transfer mechanism according to the first aspect of the
present invention includes: a transfer unit having a transfer belt;
and, a belt contact and separation assembly for bringing the
transfer belt into, and separating it away from, an electrostatic
latent image support by shifting the position of the transfer unit,
and is characterized in that the belt contact and separation
assembly includes: a plurality of transfer unit shifters that abut
the transfer unit and shift the position of the transfer unit; a
plurality of linkage members that link with the plural transfer
unit shifters, correspondingly; an elastic member for coupling the
plural linkage members; and a driver for actuating the transfer
unit shifters through the linkage members.
[0016] The transfer belt of the present invention includes one that
transfers the developer image visualized on the electrostatic
latent image support to a recording medium that is being conveyed
by the transfer belt and one that transfers the developer image
visualized on the electrostatic latent image support, directly the
transfer belt surface.
[0017] A transfer mechanism according to the second aspect of the
present invention is characterized in that, in addition to the
configuration described in the first aspect, the driver is a
solenoid.
[0018] A transfer mechanism according to the third aspect of the
present invention is characterized in that, in addition to the
configuration described in the first or second aspect, the transfer
unit shifter makes rotational movement as the driver operates.
[0019] A transfer mechanism according to the fourth aspect of the
present invention is characterized in that, in addition to the
configuration described in any one of the first through third
aspects, the driving force of the driver is directly transmitted to
a first one of the plural transfer unit shifters, and the driving
force is indirectly transmitted to the transfer unit shifters other
than the first transfer unit shifter, by way of the elastic
member.
[0020] A transfer mechanism according to the fifth aspect of the
present invention is characterized in that, in addition to the
configuration described in any one of the first through fourth
aspects, the transfer unit shifters are actuated by the driving
force of the driver to shift the transfer unit up and down, so as
to bring the transfer unit into contact with and separate it away
from, the electrostatic latent image support.
[0021] A transfer mechanism according to the sixth aspect of the
present invention is characterized in that, in addition to the
configuration described in any one of the first through fifth
aspects, the transfer unit shifters are arranged at both side ends
of the width of the transfer belt of the transfer unit.
[0022] A transfer mechanism according to the seventh aspect of the
present invention is characterized in that, in addition to the
configuration described in any one of the first through sixth
aspects, when the transfer belt is set at the home position for
separation in which the transfer belt is kept away from the
electrostatic latent image support, the first transfer unit shifter
arranged close to the driver is positioned a first distance away
from the electrostatic latent image support; the second transfer
unit shifter arranged farther from the driver than the first
transfer unit shifter is positioned a second distance away from the
electrostatic latent image support; and, the second distance is
shorter than the first distance.
[0023] A transfer mechanism according to the eighth aspect of the
present invention is characterized in that, in addition to the
configuration described in the seventh aspect, at the home position
for separation, the transfer belt is separated from the
electrostatic latent image support, keeping a uniform gap distance
across the full length of the transfer belt.
[0024] A transfer mechanism according to the ninth aspect of the
present invention is characterized in that, in addition to the
configuration described in the eighth aspect, it further comprises
a holding member for holding the transfer unit in order to assure
the uniform gap distance.
[0025] A transfer mechanism according to the tenth aspect of the
present invention is characterized in that, in addition to the
configuration described in the eighth aspect, the uniform gap
distance is at least a distance that prohibits the residual toner
on the electrostatic latent image support from transferring to the
transfer belt under the influence of the electric field applied to
the transfer belt.
[0026] An image forming apparatus according to the eleventh aspect
of the present invention is an image forming apparatus for
producing image output in accordance with a print request,
includes: an image forming portion having an electrostatic latent
image support on which a developer image is formed with a
developer; a transfer mechanism for transferring the developer
image to the transfer belt side; and, a fixing unit for fixing the
developer image transferred by the transfer mechanism, onto the
recording medium, and is characterized in that the transfer
mechanism is one of those described in the above first to tenth
aspects.
[0027] In accordance with the first aspect of the present
invention, it is possible to reliably achieve the operation of
moving the transfer belt into and out of contact with the
electrostatic latent image support.
[0028] According to the second aspect of the invention, in addition
to the effect obtained by the first aspect, it is possible to
simplify the driving mechanism for the contact and separation
movement. It is also possible to enhance the response of the
contact and separation movement of the transfer unit, even in a
high-speed printing process.
[0029] According to the third aspect of the invention, in addition
to the effect obtained by the first or second aspect, it is
possible to realize an apparatus configuration that is simple and
space-saving.
[0030] According to the fourth aspect of the invention, in addition
to the effect obtained by the first through third aspects, use of
the elastic member makes it possible to tolerate a greater degree
of parts errors and assembly errors, it is hence possible to
achieve accurate drive transmission without relying on
high-precision machining and/or high-quality assembly
technology.
[0031] According to the fifth aspect of the invention, in addition
to the effect obtained by the first through fourth aspects, this
configuration makes it possible to shift the position of the
transfer unit in a stable manner and makes it possible to easily
move the recording medium or transfer belt into and out of contact
with the electrostatic latent image support whose axis is laid out
approximately horizontal.
[0032] According to the sixth aspect of the invention, in addition
to the effect obtained by the first through fifth aspects, it
possible to shift the position of the transfer unit in a stable
manner with a structure that is space-saving and configured with a
lower number of components.
[0033] According to the seventh aspect of the invention, in
addition to the effect obtained by the first through sixth aspects,
it is possible to smoothly actuate the second transfer unit shifter
that is poor in response compared to the first transfer unit
shifter, hence move the transfer belt, reliably and uniformly, into
and out of contact with the electrostatic latent image support. It
is also possible to bring the transfer belt into contact with the
electrostatic latent image support, at the same timing across the
width.
[0034] According to the eighth aspect of the invention, in addition
to the effect obtained by the first through seventh aspects, it is
possible to achieve contact and separation movement of the transfer
belt in a reliable manner and hence effect a reliable transfer
process.
[0035] According to the ninth aspect of the invention, in addition
to the effect obtained by the first through eighth aspects, it is
possible to reliably achieve the operation of contact and
separation between the electrostatic latent image support and the
transfer belt. Further, this configuration makes it possible to
prevent the transfer belt from meandering by eliminating the twist
of the transfer unit when the transfer unit is kept away from the
electrostatic latent image support (at the home position for
separation)
[0036] According to the tenth aspect of the invention, in addition
to the effect obtained by the first through ninth aspects, when the
transfer unit is positioned at the home position for separation, no
influence of the electric field applied to the transfer belt will
affect the electrostatic latent image support.
[0037] According to the eleventh aspect of the invention, in
addition to the effect obtained by the first through tenth aspects,
it is possible to achieve stable image forming by performing a
reliable operation for contact and separation between the
electrostatic latent image support and the transfer belt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is an illustrative side view showing a transfer
mechanism configuration according to the first embodiment of the
present invention;
[0039] FIG. 2 is an illustrative plan view showing the same
transfer mechanism configuration;
[0040] FIG. 3A is an illustrative side view showing a state in
which a belt contact and separation assembly is kept away from a
transfer unit (home position for separation);
[0041] FIG. 3B is a illustrative plan view showing the belt contact
and separation assembly shown in FIG. 3A;
[0042] FIG. 3C is an illustrative side view showing a state in
which the belt contact and separation assembly pushes up the
transfer unit;
[0043] FIG. 3D is an illustrative plan view showing the belt
contact and separation assembly shown in FIG. 3C;
[0044] FIG. 4 is an illustrative view showing a state in which the
transfer unit is arranged away from the belt contact and separation
assembly (home position for separation);
[0045] FIG. 5 is an illustrative view showing a state in which the
transfer unit is arranged away from the belt contact and separation
assembly (home position for separation);
[0046] FIG. 6 is an illustrative view showing a state in which the
transfer unit is brought in contact with a photoreceptor drum (home
position for contact);
[0047] FIG. 7 is an illustrative view showing an overall
configuration of an image forming apparatus that adopts a transfer
mechanism in accordance with the second embodiment of the present
invention;
[0048] FIG. 8 is a partial detailed view showing the apparatus main
body configuration of the same image forming apparatus; and
[0049] FIG. 9 is a block diagram showing an electric controller
configuration of the same image forming apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The First Embodiment
[0050] Referring next to FIGS. 1 to 6, the embodiment of the
present invention will be described in detail.
[0051] A transfer mechanism 100 according to the present embodiment
includes a transfer unit 110 and a belt contact and separation
assembly 120 (FIGS. 1 and 2). In FIG. 1, designated at 3 is a
photoreceptor drum (electrostatic latent image support).
(Transfer Unit 110)
[0052] Transfer unit 110 has an endless transfer belt 103 for
conveying paper (recording media) (FIG. 1). Transfer unit 110
transfers the toner image (developer image) developed on the
photoreceptor drum 3 surface to the paper that is being conveyed by
the transfer belt 103.
[0053] Here, transfer belt 103 may be configured so as not to
convey the paper. That is, transfer belt 103 may be configured so
that the toner image developed on the photoreceptor drum 3 surface
is directly transferred to the transfer belt 103 surface.
[0054] Transfer unit 110 is arranged under photoreceptor drum
3.
[0055] Transfer unit 110 is laid out so that transfer belt 103 is
kept away with even or uneven distance with respect to the full
length of photoreceptor drum 3 when transfer belt 103 is positioned
out of contact with photoreceptor drum 3 (home position for
separation).
[0056] When transfer unit 110 is positioned with its transfer belt
103 in contact with photoreceptor drum 3, transfer belt 103 is
arranged so as to create a uniform transfer nip width with
photoreceptor drum 3 (home position for contact).
[0057] In FIG. 1, 101 designates a drive roller, 102 a driven
roller and 105 an elastic conductive roller.
(Belt Contact and Separation Assembly 120)
[0058] Belt contact and separation assembly 120 causes transfer
belt 103 to move into and out of contact with photoreceptor drum 3
by shifting the position of the transfer unit 110.
[0059] Belt contact and separation assembly 120 includes a
plurality of lift arms (transfer unit shifting members) 121a and
121b, a linkage subassembly 124 composed of a plurality of linkage
members 124a, 124b and a coil spring (elastic member) 123, and a
single solenoid (driver) 122 (see FIG. 3).
[0060] The lift arms are cam members that change the direction of
the drive from solenoid 122. Lift arms 121a and 121b in the present
embodiment deflect the driving force of solenoid 122, directed
horizontally, by approximately 90 degrees (including 90 degrees)
and transmit the force to the vertical direction. However, the
angle of deflection of the direction of the driving force is not
limited to approximately 90 degrees, but it can be determined as
appropriate depending on the position of attachment of solenoid
122.
[0061] Lift arms 121a and 121b abut the undersurface of transfer
unit 110 and move transfer unit 110 up and down in linkage with the
horizontal linear movement of solenoid 122. The number of the lift
arms may be any number as long as it is two or more. The detailed
configuration of lift arms 121a and 121b will be described
later.
[0062] Linkage members 124a and 124b are connected at their one end
to aforementioned lift arms 21a and 121b, respectively while the
other ends are connected to a coil spring 123. That is, linkage
members 124a and 124b are coupled by coil spring 123. The number of
linkage members may be any number as long as it is two or more.
[0063] Any elastic member can be used in place of spring 123.
Examples of the elastic member includes a coil spring, leaf spring,
volute spring, disc spring, power spring, rubber materials and the
like.
[0064] Solenoid 122 is a driving source for actuating lift arms 121
via linkage subassembly 124. Solenoid 122 has an actuating part
122a that moves forwards and backwards as the power is switched on
and off.
(Lift Arms 121)
[0065] As shown in FIGS. 3A and 3C, lift arms 121 are arranged at
plural positions along the width direction of transfer belt 103
(the direction perpendicular to the transfer belt 103's direction
of movement) at approximately the same height (approximately the
same level). In the present embodiment, two lift arms 121a and 121b
are laid out at both side ends of transfer unit 110 with respect to
the aforementioned width direction.
[0066] Hereinbelow, lift arm 121a is called first lift arm 121a and
lift arm 121b is called second lift arm 121b.
[0067] First lift arm 121a and second lift arm 121b have the almost
the same configurations, so that first lift arm 121a will be
described as an example.
[0068] First lift arm 121a is formed in an approximately L-shape.
Specifically, first lift arm 121a is composed of a connecting piece
121a1 and a lifting piece 121a2 being joined to one another at a
bent portion. This bent portion is angled at approximately 90
degrees. Formed in this bent portion is an attachment hole which is
rotatably fitted on a support axle 121c.
[0069] Support axle 121c serves as a reference point based on which
contact and separation movement between transfer unit 110 and belt
contact and separation assembly 120 is made. Accordingly, support
axle 121c is fixed at its one end to a part that will not make any
contact and separation movement. For example, support axle 121c is
fixed to the frame of transfer mechanism 100.
[0070] First lift arm 121a is attached to support axle 121c by
positioning connecting piece 121a1 downward and placing lifting
piece 121a2 approximately horizontal.
[0071] The distal end of connecting piece 121a1 is rotationally
coupled to linkage subassembly 124 by means of a support axle 124c.
Support axle 124c may be formed either on connecting piece 121a1 or
linkage subassembly 124, or may be formed separately from
connecting piece 121a1 and linkage subassembly 124.
[0072] The distal end of lifting piece 121a2 has a first abutment
C1 which abuts the bottom, designated at 110a, of transfer unit
110. The distal end of lifting piece 121b2 of second lift arm 121b
is called a second abutment C2.
[0073] First abutment C1 is formed in a circular arc shape when
viewed sectionally. This assures smooth movement of first abutment
C1 when it abuts bottom 110a and slides therealong.
(Linkage Subassembly 124)
[0074] Linkage subassembly 124 includes first arm 124a that is
coupled with first lift arm 121a and second arm part 124b that is
coupled with second lift arm 121b. Interposition of coil spring 123
between first arm part 124a and second arm part 124b enables
linkage subassembly 124 to expand and contract in its longitudinal
direction (the direction of coupling).
[0075] First arm part 124a is coupled at one end opposite to the
coil spring, to actuating part 122a of solenoid 122. With this
arrangement, the drive of solenoid 122 is directly transferred to
first arm part 124a. Here, actuating part 122a may be connected to
support axle 124c or connecting piece 121a1 of first lift arm
121a.
[0076] The driving force of solenoid 122 is transmitted to second
arm part 124b by way of coil spring 123.
[0077] Illustratively, as solenoid 122 is driven, the drive is
directly transmitted to first arm 121a that is coupled with first
arm part 124a while the drive is indirectly transmitted to second
lift arm 121b that is coupled with second arm part 124b, by way of
coil spring 123.
(Operation Timing Adjustment)
[0078] In the present embodiment, in order to adjust the operation
timings of first lift arm 121a and second lift arm 121b, the
distance between second abutment C2 that is located farther from
solenoid 122 and photoreceptor drum 3 is designed to be shorter
than the distance between first abutment C1 that is located closer
to solenoid 122 and photoreceptor drum 3 when they are set at their
retracted home position. In FIG. 3A, the distance La between first
abutment C1 and bottom 110a of transfer unit 110 and the distance
Lb between second abutment C2 and the aforementioned bottom 110a
are designated so that a relationship La>Lb holds.
[0079] In other words, the position of second abutment C2 is set to
be higher than that of first abutment C1 by the difference (Lb-La)
by attaching first lift arm 121a and second lift arm 121b with the
latter advanced from the former in phase.
[0080] The distance Lb between second abutment C2 and bottom 110a
can be adjusted by controlling, for example, the elastic force of
coil spring 123, the length of second arm part 124b and/or the
shape of second lift arm 121b. In the present embodiment, since the
first lift arm 121a and second lift arm 121b have the same
configuration, the distance Lb can be adjusted by for example, the
elastic force of coil spring 123 and/or the length of second arm
part 124b.
[0081] Here, when the distance Lb is adjusted by the shape of
second lift arm 121b, this can be done, for example by making the
length of connecting piece 121b1 shorter than that of connecting
piece 121a1, by making the bent portion of second lift arm 121b
greater than that of first lift arm 121a, and/or by other
methods.
(Operating Principle)
[0082] Next, the operation of transfer mechanism 100 according to
the present embodiment will be described with reference to the
drawings.
[0083] Normally, when transfer mechanism 100 is out of operation,
photoreceptor drum 3 and transfer belt 103 are kept away from each
other (home position for separation). The operation of transfer
mechanism 100 having a configuration in which first abutment C1 and
second abutment C2 are kept away from bottom 110a of transfer unit
110 when the are set at the home position for separation as shown
in FIG. 3A will be described.
[0084] When photoreceptor drum 3 and transfer belt 103 are caused
to abut each other by actuating transfer mechanism 100, solenoid
122 is activated so that its actuating part 122a moves forward in
the approximately horizontal direction in the drawing, as shown in
FIG. 3C. Actuating part 122a moves first arm part 124a that is
connected to itself, in the approximately horizontal direction
(rightwards in the drawing).
[0085] As first arm part 124a moves rightwards, connecting piece
121a1 of first lift arm 121a that is rotatably coupled with the
first arm part 124a sways counterclockwise. With this swaying,
first arm part 124a rotates counterclockwise and lifting piece
121a2 sways upwards.
[0086] As first arm part 124a moves, second arm part 124b is also
caused to move by way of coil spring 123 in the approximately
horizontal direction in the drawing. With this movement, connecting
piece 121b1 of second lift arm 121b that is rotatably coupled with
the second arm part 124b sways counterclockwise, whereby second arm
part 124b rotates counterclockwise and lifting piece 121b2 sways
upwards.
[0087] Both lifting pieces 121a2 and 121b2 of first and second lift
arms 121a and 121b, swaying upwards, abut bottom 110a of transfer
unit 110 and rotate further to raise transfer unit 110 by a
predetermined distance.
[0088] Transfer unit 110 moves up to the position (home position
for contact) at which transfer belt 103 comes into pressure contact
with photoreceptor drum 3 across its full length (FIG. 6). During
this movement, the difference in phase between first lift arm 121a
and second lift arm 121b are cancelled out by assembly accuracy and
machining accuracy.
[0089] At the contact home position, first lift arm 121a and second
lift arm 121b take rotated positions of the same inclination angle.
In this situation, of the phase difference between first and second
lift arms 121a and 121b, the phase difference that cannot be
canceled out by assembly accuracy and machining accuracy is
absorbed by elastic deformation (expansion and contraction,
flexion) of coil spring 123, so that both arms push transfer unit
110 against photoreceptor drum 3 with almost the same forces.
Accordingly, transfer belt 103 creates and maintains a uniform
transfer nip width with photoreceptor drum 3.
[0090] That is, even when a plurality of cams arranged in series
are actuated by driving a single solenoid 122, it is possible to
obtain a uniform nip width of a predetermined amount by bringing
transfer belt 103 into pressure contact with photoreceptor drum 3
across its full length.
[0091] When transfer belt 103 is separated from photoreceptor drum
3, solenoid 122 is operated in reverse to the action described
above to pull back actuating part 122a (retraction).
[0092] As linkage subassembly 124 is moved leftwards in the drawing
by solenoid 122, connecting piece 121a1 of first lift arm 121a that
is rotatably coupled with the first arm part 124a sways clockwise.
With this swaying, first arm part 124a rotates clockwise and
lifting piece 121a2 sways downwards.
[0093] As first arm part 124a moves, second arm part 124b is also
caused to move by way of coil spring 123 in the approximately
horizontal direction in the drawing. With this movement, connecting
piece 121b1 of second lift arm 121b that is rotatably coupled with
the second arm part 124b sways clockwise, whereby second arm part
124b rotates clockwise and lifting piece 121b2 sways downwards.
[0094] Lifting pieces 121a2 and 121b2 move down transfer unit 110
and further rotate and move away from transfer unit 110 to their
predetermined positions. That is, transfer unit 110 moves down to
the position at which transfer belt 103 is away from photoreceptor
drum 3, and first and second lift arms 121a and 121b are positioned
away from transfer unit 110.
EXAMPLE
[0095] There are at least two ways for regulating the
aforementioned difference (Lb-La).
[0096] The first regulating way is a method in which the distances
from bottom 110a of transfer unit 110 to first and second abutments
C1 and C2 are defined as distances La and Lb, as shown in FIG.
3A.
[0097] The second regulating way is a method in which the distances
between photoreceptor drum 3 and transfer belt 103 at both ends are
defined as distances La and Lb, as shown in FIG. 5.
(The First Regulating Method)
[0098] In order to realize the first regulating method shown in
FIG. 3A, two holding members 130 are provided in the frame,
designated at 100a, of transfer mechanism 100, as shown in FIG. 4.
That is, these holding members 130 support the undersurface of
transfer unit 110 so as to keep distances La and Lb from bottom
110a of transfer unit 110 to first and second abutments C1 and C2
when transfer unit 110 is positioned at the home position for
separation (the first posture).
[0099] In the first posture, transfer belt 103 creates a gap with a
uniform gap distance L0 from photoreceptor drum 3 across the belt
width, as shown in FIG. 4.
[0100] In the first posture, the differential distance (Lb-La) is
formed while no load is being acted on second abutment C2.
Accordingly, it is possible to adjust the position of second
abutment C2 so as to create the necessary differential distance by
controlling the elastic force of coil spring 123, the length of
second arm part 124b and/or the shape of second lift arm 121b, for
instance.
[0101] A pair of holding members 130 shown in FIG. 4 are projected
approximately perpendicularly from the surfaces of frame 100a and
arranged at the same position with respect to the transfer belt
103's direction of conveyance.
[0102] Holding members 130 should not be limited as to their shape,
number and position as long as they can support transfer unit 110.
For example, holding member 130 may be a pin element, bar element,
projected structure, step or the like. The number of holding
members 130 is not particularly limited, one piece, a pair or a
plurality of holding members may be used.
[0103] According to the first regulating method, it is possible to
make the movement of transfer unit 110 by approximately vertical
translation. As a result it is possible to achieve the movement for
contact and separation between photoreceptor drum 3 and transfer
belt 103 in a reliable manner.
[0104] Further, provision of holding members 130 enables transfer
unit 110 to keep the same posture when it is at the home position
for separation and when it is at the home position for contact. As
a result, the movement from the home position for separation to the
home position for contact can be done by a mere translation of
transfer belt 103, so that it is possible to prevent meander of
transfer belt 103, which would occur if the posture of transfer
unit 110 was changed.
(The Second Regulating Method)
[0105] The second regulating method shown in FIG. 5 can he realized
by constantly supporting bottom 110a of transfer unit 110 with
first and second lift arms 121a and 121b (the second posture).
Accordingly, transfer unit 110 moves up and down (comes into and
out of contact) in conformity with the rotations of first and
second lift arms 121a and 121b.
[0106] Since the second regulating method does not need any
supporting member 130 the structure can be made simple.
[0107] In the second posture, the differential distance (Lb-La) is
created when a load (transfer unit 110) is acting on second
abutment C2. Accordingly, it is possible to adjust the position of
second abutment C2 so as to create this differential distance, by
controlling the elastic force of coil spring 123, the length of
second arm part 124b and/or the shape of second lift arm 121b, for
example.
(Effect)
[0108] According to the present embodiment, the moving range of
second lift arm 121b that is located farther from solenoid 122 is
made narrower than that of first lift arm 121a that is located
closer to solenoid 122, with respect to the direction (vertical
direction) in which the transfer unit 110 moves when coming into
and out of contact. Accordingly, it is possible to reliably bring
transfer belt 103 into and out of contact with photoreceptor drum 3
across its full length even when the configuration involves
machining errors and assembly errors. Further, if there is a delay
in action of second lift arm 121b that is located far from the
actuating point (solenoid 122), the arrival of second lift arm 121b
at bottom 110a of transfer unit 110 can be synchronized with that
of the first lift arm by delaying the arrival of first lift arm
121a at bottom 110a of transfer unit 110 by virtue of the
difference in range of movement.
[0109] Further, in the present embodiment, as a configuration of
linkage subassembly 124, first arm part 124a that is coupled to
first lift arm 121a and second arm part 124b that is coupled to
second lift arm 121b are connected by coil spring 123. Accordingly,
with respect to the difference in range of movement between first
lift arm 121a and second lift arm 121b, the differential range of
movement that cannot be canceled by assembly accuracy and machining
accuracy can be absorbed by elastic deformation (expansion and
contraction, flexion) of coil spring 123. As a result, first lift
arm 21a and second lift arm 121b push transfer unit 110 with
approximately equivalent forces so as to create and maintain a
uniform transfer nip width between transfer belt 103 and
photoreceptor drum 3.
[0110] Further, machining errors and assembly errors can be
absorbed by the repulsive force of elastic member 123. Accordingly,
the above operation of first and second lift arms 121a and 121b can
be made reliable, so that it is possible to reliably achieve the
operation for contact and separation between the transfer belt and
photoreceptor drum 3.
[0111] When the first posture is adopted to create the difference
in the moving range, the vertical movement of transfer unit 110
across the paper width can be achieved essentially by a
translation. Accordingly, it is possible to reliably achieve the
operation for contact and separation between transfer belt 103 and
photoreceptor drum 3. Further, since transfer belt 103 can be
supported approximately horizontal when transfer unit 110 is
retracted, it is possible to avoid the transfer unit being twisted,
hence prevent transfer belt 103 from meandering. As a result,
stable paper conveyance can be assured, and this realizes highly
qualified image output.
[0112] On the other hand, use of the second regulating method
(second posture) makes holding members 130 unnecessary, hence the
configuration of transfer mechanism 100 can be simplified.
[0113] It should be noted that the elastic member of the present
invention may use other spring elements and rubber materials,
instead of the aforementioned coil spring 123, as long as it can
present an elastic function.
[0114] Furthers the embodiment is constructed so that abutment
between photoreceptor drum 3 and transfer belt 103 is performed by
moving actuating part 122a of solenoid 122 forwards while
separation between photoreceptor drum 3 and transfer belt 103 is
performed by moving actuating part 122a backwards. However, the
actuating part may be moved in a reverse manner. That is,
separation between photoreceptor drum 3 and transfer belt 103 may
be performed by moving actuating part 122a forwards while abutment
between photoreceptor drum 3 and transfer belt 103 may be performed
by moving actuating part 122a backwards.
The Second Embodiment
[0115] Next, an image forming apparatus 1A including a transfer
mechanism 100 according to the present invention will be described
in detail with reference to the drawings.
[0116] FIG. 7 is an illustrative view showing the overall
configuration of an image forming apparatus using a transfer
mechanism according to the second embodiment of the present
invention and FIG. 8 is a partial detailed view showing the
configuration of the apparatus main body of the image forming
apparatus.
[0117] Image forming apparatus 1A according to the present
embodiment is an image forming apparatus that includes an image
forming portion 14, transfer mechanism 100 and a fixing unit
(fixing device) 6, and produces image output in response to a print
request.
[0118] Image forming portion 14 includes a photoreceptor drum 3 on
which a developer image (toner image) is formed with a developer
(toner).
[0119] Transfer mechanism 100 employs the transfer mechanism of the
present invention and includes the above-described transfer unit
110 and the above-described belt contact and separation assembly
120.
[0120] Fixing unit 6 fixes the toner image that was transferred on
paper P to paper P.
[0121] To being with, the overall configuration of image forming
apparatus 1A according to the present embodiment will be described
with reference to the drawings.
[0122] As shown in FIGS. 7 and 8, image forming apparatus 1A is
essentially composed of an apparatus main body 1A1 and an automatic
document processor 1A2.
[0123] Apparatus main body 1A1 essentially includes a light
exposure unit 1, a developing unit 2, a photoreceptor drum 3, a
charger 4, a charge erasing device 41, a cleaner unit 5, a fixing
unit 6, a paper feed path 7, a paper feed tray 8, a paper output
tray 9, a transfer mechanism 100 and the like.
[0124] Arranged on the top surface of apparatus main body 1A1 is an
original placement table 21 made of transparent glass on which a
document is placed. Automatic document processor 1A2 is arranged on
the top of this original placement table 21 so that it can
pivotally open upwards. On the other hand, a scanner portion 22 as
a document reader for reading image information of originals is
laid out under this original placement table 21.
[0125] Arranged below scanner portion 22 are light exposure unit 1,
developing unit 2, photoreceptor drum 3, charger 4, charge erasing
device 41, cleaner unit 5, fixing unit 6, paper feed path 7, paper
output tray 9 and transfer mechanism 100. Further, paper feed tray
8 for accommodating paper P is arranged under these components.
[0126] Light exposure unit 1 emits a laser beam in accordance with
the image data (print image information) output from an
unillustrated image processor to irradiate the photoreceptor drum 3
surface that has been uniformly charged by charger 4. In this way,
light exposure unit 1 writes and forms an electrostatic latent
image corresponding to the image data on the photoreceptor drum 3
surface.
[0127] Light exposure unit 1 is arranged directly under scanner
portion 22 and above photoreceptor drum 3. Light exposure unit 1
includes laser scanning units (LSUs) 13a and 13b each having a
laser emitter 11 and a reflection mirror 12. In the present
embodiment, in order to achieve high-speed printing operation, a
method for alleviating a rush of irradiation timings by using a
multiple number of laser beams, namely a two-beam method, is
adopted.
[0128] Here, in the present embodiment laser scanning units (LSUs)
13a and 13b are used for light exposure unit 1, but an array of
light emitting elements, e.g., an EL or LED writing head may be
used.
[0129] Photoreceptor drum 3 has a cylindrical shape and is arranged
under light exposure unit 1 as shown in FIG. 8. Photoreceptor drum
3 is controlled so as to rotate in a predetermined direction (in
the direction of arrow A in the drawing) by a drive controller 62
(FIG. 9). Arranged starting from the position at which image
transfer ends downstream in the rotational direction of the
photoreceptor drum along the peripheral surface of this
photoreceptor drum 3 are a paper separation claw 31, cleaner unit
5, charger 4 as an electric field generator, developing unit 2 and
a charge erasing device 41 in the order mentioned.
[0130] Paper separation claw 31 is disposed so as to be moved into
and out of contact with the outer peripheral surface of
photoreceptor drum 3 by means of a solenoid 32. This paper
separation claw 31, when it is put in abutment with the outer
peripheral surface of photoreceptor drum 3, functions to peel off
the paper P that has adhered to the photoreceptor drum 3
surface.
[0131] As a driver for paper separation claw 31, a drive motor or
the like may be used instead of solenoid 32, or any other driver
may also be selected.
[0132] Developing unit 2 visualizes the electrostatic latent image
formed on photoreceptor drum 3 with black toner. Developing unit 2
is arranged at approximately the same level at the side (on the
right side in the drawing) of photoreceptor drum 3 downstream of
charger 4 with respect to the rotational direction of the
photoreceptor drum (in the direction of arrow A in the drawing). A
registration roller 15 is disposed under this developing unit
2.
[0133] Registration roller 15 is operated and controlled by a
driver 66 (FIG. 9) and controller 62 so as to convey the paper P
delivered from paper feed tray 8 (FIG. 7) into and between
photoreceptor drum 3 and transfer belt 103 whilst making the
leading end of the paper P register with the toner image on the
photoreceptor drum 3.
[0134] Charger 4 is a charging portion for uniformly charging the
photoreceptor drum 3 surface at a predetermined potential. Charger
4 is arranged over photoreceptor drum 3 and close to the outer
peripheral surface thereof.
[0135] Here, a discharge type charger 4 is used in the present
embodiment, but a contact roller type or a brush type may be
used.
[0136] Charge erasing device 41 is a pre-transfer erasing portion
for lowering the surface potential of the photoreceptor drum 3 in
order to facilitate the toner image formed on the photoreceptor
drum 3 surface to transfer to paper P. Charge erasing device 41 is
laid out on the downstream side of developing unit 2 with respect
to the photoreceptor drum's direction of rotation and under the
photoreceptor drum 3 and close to the outer peripheral surface of
the same.
[0137] Though in the present embodiment, charge erasing device 41
is configured using a charge erasing electrode, a charge erasing
lamp or any other method for erasing charge can be used instead of
the charge erasing electrode.
[0138] Cleaner unit 5 removes and collects the toner left on the
surface of photoreceptor drum 3 after development and image
transfer. Cleaner unit 5 is disposed at approximately the same
level at the side of photoreceptor drum 3 (on the left side in the
drawing), on the approximately opposite side across photoreceptor
drum 3 from developing unit 2.
[0139] As described above, the visualized electrostatic image on
photoreceptor drum 3 is transferred to the paper P to which
transfer mechanism 100 applies an electric field having an opposite
polarity to that of the electrostatic image.
[0140] For example, when the electrostatic image bears negative (-)
charge, the applied polarity of transfer mechanism 100 should be
positive (+).
[0141] Transfer mechanism 100 is one that was described in the
first embodiment and includes transfer unit 110 and belt contact
and separation assembly 120.
[0142] As shown in FIG. 8, transfer unit 110 is a transfer belt
unit in which transfer belt 103 having a predetermined resistivity
(ranging from 1.times.10.sup.9 to 1.times.10.sup.13.OMEGA.cm in
this embodiment) is wound and tensioned on a drive roller 101, a
driven roller 102 and other rollers.
[0143] Transfer unit 110 is disposed under photoreceptor drum 3
with the transfer belt 103 surface put in contact with part of the
outer peripheral surface of photoreceptor drum 3. This transfer
belt 103 is adapted to convey paper P while pressing the paper
against photoreceptor drum 3. As already mentioned in the first
embodiment, transfer belt 103 is not limited to the configuration
that conveys paper P, but it can be applied to a configuration that
does not convey paper P.
[0144] Arranged under transfer unit 110 is belt contact and
separation assembly 120.
[0145] Belt contact and separation assembly 120 has the same
configuration as in the configuration of the first embodiment
described above. That is, belt contact and separation assembly 120
includes lift arms 121 that abut transfer unit 110 and shift the
position of transfer unit 110, a plurality of linkage members each
being linked with corresponding lift arm 121 and a coil spring 123
for connecting multiple linkage members and a solenoid 122 for
actuating lift arms 121 by way of linkage members.
[0146] In this belt contact and separation assembly 120, solenoid
122 is operated in accordance with a processing signal (operation
signal) input to image forming apparatus 1A. When the toner image
on photoreceptor drum 3 is transferred to paper P (or transfer belt
103), solenoid 122 is operated so as to bring transfer belt 103
into contact with photoreceptor drum 3. When no transfer process is
done, solenoid 122 is operated in reverse so as to separate
transfer belt 103 from photoreceptor drum 3.
[0147] An elastic conductive roller 105 having a conductivity
different from that of drive roller 101 and driven roller 102 and
capable of applying a transfer electric field is laid out at a
contact point 104 where transfer belt 103 comes into contact with
photoreceptor drum 3.
[0148] Elastic conductive roller 105 is composed of a soft material
such as elastic rubber, foamed resin etc. This elasticity of
elastic conductive roller 105 permits photoreceptor drum 3 and
transfer belt 103 to come into, not line contact, but area contact
of a predetermined width (called a transfer nip) with each other.
This area contact makes it possible to improve the efficiency of
transfer to the paper P that is being conveyed.
[0149] Further, a charge erasing roller 106 is disposed on the
interior side of transfer belt 103, on the downstream side, with
respect to the direction of paper conveyance, of the transfer area
of transfer belt 103. Charge erasing roller 106 erases the electric
field applied to the paper being conveyed through the transfer area
so as to achieve smooth conveyance of paper P to the subsequent
stage.
[0150] Also in transfer mechanism 100, a cleaning unit 107 and a
plurality of charge erasing devices 108 are provided. Cleaning unit
107 removes dirt due to leftover toner on transfer belt 103. Charge
erasing devices 108 erase electricity on transfer belt 103. Erasure
of charge by erasing devices 108 may be performed by grounding the
transfer belt via the apparatus or by positively applying charge of
a polarity opposite to that of the transfer field to the transfer
belt.
[0151] The paper P with a static image (unfixed toner) transferred
thereon by transfer mechanism 100 is conveyed to fixing unit 6,
where it is pressed and heated so as to fuse the unfixed toner and
fix it to the paper P.
[0152] As shown in FIG. 8, fixing unit 6 includes a heat roller 6a
and a pressing roller 6b. As heat roller 6a is rotated with paper P
being held between these heat roller 6a and pressing roller 6b,
paper P passes through and between heat roller 6a and pressing 6b
while it is heated and pressed. In this process, the toner image
transferred on paper P can be fused and fixed thereto.
[0153] Arranged on the downstream side of fixing unit 6 with
respect to the direction of paper conveyance is a conveyance roller
16 for conveying paper P.
[0154] Heat roller 6a has a sheet separation claw 611, a roller
surface temperature detector (thermistor) 612 and a roller surface
cleaning member 613, arranged on the outer periphery thereof. A
heat source 614 for heating the heat roller surface at a
predetermined temperature (set fixing temperature: approximately
160 to 200 deg. C.) is provided inside heat roller 6a.
[0155] Arranged on the outer periphery of pressing roller 6b is a
pressing member 621 which presses both ends of pressing roller 6b
so that pressing roller 6b abuts heat roller 6a with a
predetermined pressure. Also, a sheet separation claw 622 and a
roller surface cleaning element 623 are provided on the outer
periphery of pressing roller 6b, similarly to the outer periphery
of heat roller 6a.
[0156] In this fixing unit 6, as shown in FIG. 8 the unfixed toner
on the paper P being conveyed is heated and fused by heat roller
6a, at the pressed contact (so-called fixing nip portion) 600
between heat roller 6a and pressing roller 6b, so that the unfixed
toner is fixed to the paper P by its anchoring effect to the paper
P by the pressing force from heat roller 6a and pressing roller
6b.
[0157] Paper feed tray 8 (FIG. 7) can accommodate a stack of sheets
(paper) to which image information will be output (printed). Paper
feed tray 8 is arranged under image forming portion 14 made up of
light exposure unit 1, developing unit 2, photoreceptor drum 3,
charger 4, charge erasing device 41, cleaner unit 5, fixing unit 6
etc. A paper pickup roller 8a is disposed at an upper position on
the paper delivery side of this paper feed tray 8.
[0158] This paper pickup roller 8a (FIG. 7) picks up paper P, sheet
by sheet, from the topmost of a stack of paper stored in paper feed
tray 8, and conveys the paper downstream (for convenience' sake,
the delivery side of paper P (the cassette side) is referred to as
upstream and the direction of conveyance is referred to as
downstream). That is, paper pickup roller 8a conveys paper P to the
registration roller (also called "idle roller") 15 side in paper
feed path 7.
[0159] Since the image forming apparatus 1A according to the
present embodiment is aimed at performing high-speed printing
operations, a multiple number of paper feed trays 8 each capable of
stacking 500 to 1500 sheets of standard-sized paper P are arranged
under image forming portion 14. Further, a large-capacity paper
feed cassette 81 capable of storing multiple kinds of paper in
large volumes is arranged at the side of apparatus 1A. Also, a
manual feed tray 82 for mainly supporting printing etc. for
irregular sized paper is arranged over the large-capacity paper
feed cassette 81.
[0160] Paper output tray 9 is arranged on the opposite side across
the apparatus from that of manual feed tray 82. Also, apparatus 1A
may include, instead of paper output tray 9, a post-processing
machine for output paper (machine for stapling, punching and other
tasks) and/or a multi-bin paper output tray etc., as an option.
[0161] Paper feed path 7 is laid out between the aforementioned
photoreceptor drum 3 and paper feed tray 8, and conveys paper P
supplied from paper feed tray 8, sheet by sheet, to transfer
mechanism 100. In transfer mechanism 100 a toner image is
transferred from photoreceptor drum 3 to the paper, which is
conveyed to fixing unit 6. The paper with an unfixed toner image
fixed thereon in fixing unit 6 is then conveyed by an inversion
conveyance roller 18 and a switch back roller 19, along the paper
feed paths and branch guides, set for the designated processing
mode.
[0162] Next, the control system of image forming apparatus 1A
according to the present embodiment will be described in detail
with reference to the drawings.
[0163] FIG. 9 is a block diagram showing an electric controller
configuration of the image forming apparatus according to the
present embodiment.
[0164] As shown in FIG. 9, the image forming apparatus 1A according
to the present embodiment performs processes such as image reading,
image processing, image forming and conveyance of paper P, etc., by
a central processing unit (CPU) 54 in accordance with the program
stored beforehand in a ROM (read only memory) 55, using temporal
storage such as a RAM (random access memory) 56 etc.
[0165] Here, it is also possible to use other storage means such as
a HDD (hard disk drive) etc., instead of ROM 55 and RAM 56.
[0166] In image forming apparatus 1A, the image information of an
original (original image data) captured by scanner portion 22, or
original image information transmitted from other terminal devices
connected on an unillustrated communication network, is adapted to
be input to an image processor 57 by way of a communication
processor 58.
[0167] Image processor 57 shapes the original image information
stored in the storage such as RAM 56 or the like into printing
image information that is suitable for printing (image forming onto
paper), in accordance with the aforementioned program.
[0168] The printing image information is input to image forming
portion 14.
[0169] Image forming portion 14, a paper conveying portion
(performing various detentions and controls of the paper in paper
feed path 7 etc.) 59, fixing unit 6 and paper discharge processor
(performing various detections and controls of the paper in paper
discharge path 17) 60 are linked with respective components of
drive controller 62.
[0170] The paper conveyed by paper conveying portion 59 advances
through the printing stage (the printing process of image
information in image forming portion 14) and then a fixing stage
(fixing unit 6) for the printed paper P and is discharged to the
paper discharge portion (paper output tray 9).
[0171] Here, paper conveying portion 59 is adapted to receive
detection signals from a pre-registration detection switch 596, an
unillustrated fixing detection switch and paper discharge detecting
switch etc.
[0172] Pre-registration detection switch 596 is a switch that
detects whether the paper reaches registration roller 15. The
fixing detection switch is a switch that detects whether the paper
reaches fixing unit 6. The paper discharge detecting switch is a
switch that detects whether the paper has been discharged.
[0173] Image forming apparatus 1A further has an operational
condition setter 77.
[0174] This operational condition setter 77 sets up operational
conditions for image forming and conditions of conveyance etc., in
image forming apparatus 1A, in accordance with the image forming
request or the image forming conditions such as the type of
recording media (paper) etc., designated by the user through
control switches 76.
[0175] Further, in image forming apparatus 1A, based on the set
operating conditions, an original reading driver 64, a paper
conveyance driver 66, an inversion conveyance driver 67, a printing
process driver 68, a transfer mechanism driver 100A, a fixing
driver 70, a paper discharge driver 72 and large-volume paper feed
cassette (paper feed unit) 81 are operated following the
instructions from CPU 54 in accordance with the program stored in
ROM 55 so that these drivers can operate in synchronization.
[0176] Original reading driver 64 is a drive actuator for the
reading portion (scan portion 22).
[0177] Paper conveyance driver 66 is a drive actuator for paper
conveying portion 59, specifically, drive motors for paper pickup
roller 8a and registration roller 15 arranged along the
aforementioned paper feed path 7.
[0178] Inversion conveyance driver 67 includes drive motors for
inversion conveyance roller 18 and switch back roller 19.
[0179] Printing process driver 68 is a drive actuator for image
forming portion 14 and the like, and its example is a drive motor
for photoreceptor drum 3.
[0180] Transfer mechanism driver 100A is a drive actuator for
transfer mechanism 100 etc.
[0181] Fixing driver 70 is of drive motors for heat roller 6a and
pressing roller 6b in fixing unit 6.
[0182] Paper discharge driver 72 is a drive actuator for paper
discharge processor 60 etc., including drive motors for paper
discharge roller 17, etc.
[0183] The drive sources of the drive motors for all these drivers
may be provided as common or different drive motors with
appropriate power transmission mechanisms.
[0184] Transfer mechanism driver 101A includes solenoid 122 for
moving transfer unit 110 into and out of contact with photoreceptor
drum 3. Transfer mechanism driver 101A performs its operation in
synchronism with the operation of drive roller 101 of transfer belt
103 and the operations of paper conveyance driver 66, printing
process driver 68, etc.
[0185] Further, image forming apparatus 1A may be used with
optional configurations 74 including post-processors (stapler,
puncher, multi-bin paper output trays, shifter, etc.), automatic
document reader (automatic document processor 1A2 etc.),
large-volume paper feed cassette 81 and the like. These optional
configurations 74 incorporate individual controllers 74a separately
from the controller of image forming apparatus 1A so that each
processor can operate in synchronization with the main apparatus by
performing timing adjustment via the aforementioned communication
processor 58.
[0186] A recording medium detecting portion 78 detects arrival of
the leading end of the paper at fixing unit 6 or the output
portion. Specifically, recording medium detecting portion 78
includes: a conveyance time measuring portion 79a and a conveyance
timing determining portion 79b.
[0187] Conveyance time measuring portion 79a measures the time for
conveyance of the paper from when the paper is delivered from
registration roller 15 at the entrance of paper feed path 7 where
the paper is introduced.
[0188] Conveyance timing determining portion 79b determines the
timings at which the paper is conveyed in paper feed path 7, based
on the distances from registration roller 15 to fixing unit 6 and
discharge roller 17 to be controlled, and the paper's speed of
conveyance.
[0189] In this embodiment recording medium detecting portion 78 is
adapted to detect the timings at which the paper arrives at (enter)
fixing unit 6 and paper discharge roller 17 based on the conveyance
timing of recording medium detected by conveyance timing
determining portion 79b.
[0190] According to the present embodiment as described heretofore,
use of transfer mechanism 100 according to the present invention
for image forming apparatus 1A assures a reliable operation of
contact and separation between photoreceptor drum 3 and transfer
belt 103, hence making it possible to achieve stable transfer and
paper conveyance. Thus, this configuration contributes to
realization of high quality image output.
[0191] Further, according to the present embodiment, it is possible
to reliably achieve the operation of contact and separation between
photoreceptor drum 3 and transfer belt 103 at suitable timing
without keeping transfer belt 103 in continuous contact with
photoreceptor drum 3. As a result, it is possible to prevent
photoreceptor drum 3 and transfer belt 103 from being worn out,
hence making it possible to lengthen the lives of these
components.
[0192] It should be noted that the present invention is not limited
to the image forming apparatus illustrated in the above embodiment,
and the present invention can be developed into image forming
apparatus having different configurations from the present
embodiment as long as it includes an equivalent transfer mechanism
or a configuration akin to that.
* * * * *